This request is for funds to purchase a dual line Nikon multiphoton system equipped with a resonant and galvonometer driven scan head and 4 GaAsP detectors. This instrument will be housed within the Center for Biologic Imaging (CBI) at the University of Pittsburgh School of Medicine. The mandate of this core facility is to provide access to a full range of light and electron optical, image analysis, and morphometric methods to all research groups within the University of Pittsburgh School of Medicine. Multiphoton microscopy is an essential service provided by the center. Currently the Center is equipped with two multiphoton systems, a galvonometer driven FV1000 purchased in 2009 and a galvonometer/resonant scanning Nikon A1R purchased in 2011. The FV1000 is heavily used for second harmonic imaging and deep tissue imaging of fixed samples. However, as it is a slow scanning system, with tradional PMTS and a basic motorized stage, none of which can be upgraded, it is not useable for the majority of projects that fundamentally need multiphoton technology. We believe use of the newer A1R is at saturation (used over 2500 hours in the last 12 months). This application is requesting funds fo purchase a second A1R system to meet the growing needs of an expanding, well supported user group. The need for this instrument is demonstrated in this application with several diverse NIH supported projects in fields including; Immunology, Transplant immunology, Neurobiology, Pulmonary medicine, and Developmental biology. All of which have extensive preliminary data demonstrating need for high speed, intravital living system imaging as well as defining a clear need for a two line laser. Since the CBI commenced operations 25 years ago, it has become an integral part of the medical research community currently participating in research projects with more than 300 PHS funded groups within the medical area, as well as in PHS supported projects with investigators in other departments and at neighboring institutions. The steering committee of the CBI feel that acquistion of another basic highspeed multiphoton system as an essential addition to the repertoire of instrumentation available to PHS funded users of the Center.